Oxygenates and processes for their manufacture

ABSTRACT

Alcohols suitable for plasticizer ester manufacture and acids are made by cofeeding olefins to oxonation, aldolizing the resulting aldehyde and hydrogenating the resulting unsaturated aldehydes, optionally dehydrating a part of the alcohol thereby made and returning the resulting olefin to oxonation, or oxidizing the aldehydes.

This is the U.S. National Stage Application of PCT/EP96/00162 filed Jan.7, 1996 now WO 96/22264 published Jul. 25, 1996.

FIELD OF THE INVENTION

This invention relates to a process for the manufacture of aldehydes,alcohols, acids, and esters, the use of the latter as syntheticlubricants, as plasticizers, to polymeric compositions plasticized bythe esters, and to products made from the compositions.

BACKGROUND OF THE INVENTION

The esters of 2-ethylhexanol, especially the phthalate, are among themost commonly used plasticizers. The alcohol is obtainable by, forexample, subjecting propene to hydroformylation, dimerizing theresulting butanal by the aldol reaction, a term which is used throughoutthis specification, including the claims, as including the subsequentdehydration to an unsaturated aldehyde, and hydrogenating the resultingaldehyde to form a saturated alcohol.

The propene, produced for example by a steam cracking plant, has to bepurified before hydroformylation, and its cost as feedstock is increasedas a result.

There accordingly remains a need for an alternative route tocommercially useful organic molecules, and more especially one that iscapable, if desired, of producing a single isomeric product or apreponderant proportion of one or two isomers.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a process for the manufacture of at leastone higher aldehyde, higher alcohol, or a higher acid, from a lowerhydrocarbon,

which comprises hydroformylating two different ethylenically unsaturatedhydrocarbons to form a first aldehyde and a second aldehyde, thehydrocarbons being hydroformylated separately or in admixture and, ifthe latter, if desired or required at least partially separating thefirst aldehyde from the second aldehyde,

subjecting the first aldehyde, if desired in admixture with the second,to aldolization, hydrogenating at least a portion of the resultingunsaturated aldehyde or aldehydes to form a corresponding higher alcoholor alcohols, and, if only a portion is so hydrogenated, optionallyselectively hydrogenating a further portion of the unsaturated aldehydeto form a corresponding saturated higher aldehyde, optionally oxidizingit to form a corresponding higher acid,

optionally dehydrating a portion of the higher alcohol or of the higheralcohols to form at least one ethylenically unsaturated hydrocarbon andreturning it to hydroformylation, and

optionally recovering the second aldehyde as higher aldehyde,hydrogenating it to form a higher alcohol, or oxidizing it to form ahigher acid.

Advantageously, the process includes returning unsaturated hydrocarbonproduced by dehydration to oxonation. It is within the scope of theinvention to return unsaturated aldehyde to aldolization, although thisis not at present preferred.

More especially, in a first aspect, the present invention provides aprocess comprising

(a) subjecting a composition comprising two ethylenically unsaturatedhydrocarbons having differing numbers of carbon atoms, carbon monoxide,and hydrogen to hydroformylation conditions to form a compositioncomprising at least a lower aldehyde and a higher aldehyde,

(b) at least partially separating the lower and higher aldehydes, toform a lower aldehyde-containing composition and a higheraldehyde-containing composition,

(c) subjecting the lower aldehyde-containing composition to aldolcondensation, and, optionally,

(d) hydrogenating the unsaturated aldehyde resulting from the aldolcondensation to form a first alcohol and, optionally, dehydrating atleast a portion of the first alcohol to form an ethylenicallyunsaturated hydrocarbon, and optionally returning the resultingethylenically unsaturated hydrocarbon to hydroformylation, andoptionally hydrogenating the higher aldehyde-containing composition toform a second alcohol and optionally esterifying the first, the second,or both the first and second alcohols separately or together.

Advantageously the two unsaturated hydrocarbons subjected tohydroformylation are such that the resulting lower and higher aldehydesare readily separable by, for example, distillation.

Except where the context otherwise requires, the features of the firstaspect said below to be advantageous are advantageous in all aspects ofthe invention, especially the specifically listed succeeding aspects.

Advantageously, return of the ethylenically unsaturated hydrocarbonresulting from dehydration to the hydroformylation step in the processtakes place when it has the same number of carbon atoms as one of thefeedstock hydrocarbons and preferably, when there are only two, thehydrocarbon having the higher number of carbon atoms. If it differs fromboth the feedstock hydrocarbons it is advantageously transferred to aparallel operation, carrying out a process on a hydrocarbon feed towhich it is identical. It is, however, although not presently preferred,within the scope of the invention to carry out the process withunsaturated hydrocarbons having three or more different carbon numbers.

DETAILED DESCRIPTION OF THE INVENTION

As examples of unsaturated hydrocarbons to be treated by the process ofthe invention there may be mentioned, more especially, olefins, andadvantageously olefins having from 2 to 20 carbon atoms.

The invention is especially applicable to treating a mixture of a lower,C₂ to C₄, and a higher, C₅ to C₂₀, olefin. As lower olefins there may bementioned ethylene, propene, n-butene and 2-methylpropene. As higherolefins there may be especially be mentioned single isomeric olefinfeeds, for example, pentene-1, hexene-1 and their higher homologues, ormixtures of linear and branched olefin isomers predominantly of the samecarbon number. An example of the latter is a hexene feed, which maycontain 2-methylpentene-1, 2-methylpentene-2-, cis- andtrans-4-methylpentene-2, 4-methylpentene-1, cis- and trans-hexene-3,cis- and trans-hexene-2, 2,3-dimethylbutene-2, 2-ethylbutene-1 andtrans-3-methylpentene-2. Usually olefin feeds of this nature alsocontain varying amounts of the corresponding alkanes.

The invention is more especially applicable to treating a mixture ofethylene and higher e.g., C₅ and above, alkenes, especially hexenes,especially 2-methylpentene-1.

On subjecting such a mixture to hydroformylation, a mixture of C₃ and C₇saturated aldehydes results; on subjecting the C₃ aldehyde toaldolization an unsaturated C₆ aldehyde results. This may, if desired,be selectively hydrogenated to a C₆ saturated aldehyde, which may inturn be hydrogenated to a C₆ alcohol, or oxidized to form a C₆ acid. Thealcohol, or a portion thereof, may be dehydrated to hexene, which willlargely be 2-methylpentene-1 and -2, which may be recycled to thehydroformylation stage. Accordingly, from the C₆ and C₇ saturatedaldehydes there may be produced the corresponding alcohols and theiresters, or the corresponding acids and their esters.

The invention accordingly provides a means of obtaining C₆ and C₇products from ethylene as the sole hydrocarbon starting material.

In an advantageous embodiment of the first aspect of the invention,there is accordingly provided a process comprising hydroformylating acomposition comprising ethylene and a 2-methylpentene, separating theresulting C₃ aldehyde and C₇ aldehydes, aldolizing the C₃ aldehyde,hydrogenating the resulting C₆ unsaturated aldehyde to form an alcohol,dehydrating the alcohol to form a composition comprising a2-methylpentene, returning the composition to the hydroformylationstage, and recovering a product comprising a C₇ aldehyde.

The 2-methylpentene may be a mixture of isomers, advantageouslypredominantly 2-methylpentene-1 and -2.

U.S. Pat. No. 4,426,542 discloses dimerizing propene, oxonating theresulting hexenes to heptanals, hydrogenating to heptanois, dehydratingto heptenes and oxonating the heptenes, the octanals resulting beingaldolized in turn with hexanal and hydrogenated to form inter alia a C₁₄alcohol.

U.S. Pat. No. 4,262,142 discloses the low pressure hydroformylation ofmixtures of ethylene and an alpha-olefin having from 3 to 20 carbonatoms using a rhodium-based catalyst, while GB-A-1,120,277 discloseshydroformylating ethylene and propene under high pressure using acobalt-based catalyst. In the U.S. patent, it is pointed out that underthe conditions of the British patent propene conversion is adverselyaffected by the presence of ethylene; this disadvantage is avoided whena rhodium-based catalyst is employed. In the hydroformylation process ofthe present invention, however, a cobalt catalyst is advantageouslyused.

The composition treated in step (a) of the first aspect of the presentinvention comprises as essential ingredients carbon monoxide, hydrogen,and two unsaturated hydrocarbons. In a preferred embodiment of theinvention, one hydrocarbon is ethylene, and the second hydrocarbon isprovided by recycling, as described above, either from the same processor a similar process using different starting materials. For clarity,the invention will be described in more detail below with referencesolely to ethylene and a second, recycled, hydrocarbon, but it will beappreciated that, mutatis mutandis, the procedures apply to otherfeedstocks.

The components of the composition not obtained by recycling may beobtained by numerous methods, including mixing pure C₂H₄, CO and H₂,mixing purified commercially produced C₂H₄ with purified synthesis gas(syngas) or as the direct or purified product of a steam crackingfurnace. The composition is, however, conveniently a dilutemulti-component syn gas (DMCS) stream, by “dilute ” being meant that thestream has not been completely purified by the removal of diluents,e.g., methane and ethane, that do not take part in the hydroformylationreaction. The stream may result from treatment of natural gas, e.g.,from the mixture of a first stream containing CO and H₂ produced by aconventional partial oxidation (POX) technology and a second streamcontaining ethylene. Ethylene may be obtained from any of a number ofsources, inter alia, from ethane, which is also obtainable from naturalgas; another route to ethylene is by methane pyrolysis.

Depending on the source, the DMCS will contain, as indicated above, H₂,CO and one or both C₂ unsaturated hydrocarbons, and in additiondifferent neutral and undesired species.

The DMCS composition, as far as concerns neutral and essentialcomponents, is advantageously as follows in molar terms:

CO: 5 to 33%, preferably 10 to 33%, of gas.

C₂H₄: up to 100% of CO.

H₂: from, at minimum, the molar equivalent of the ethylenicallyunsaturated species, to a maximum of 60% of DMCS. A preferred maximum istwice the molar equivalent of ethylenically unsaturated species.

Sum of alkanes, CO₂, N₂, and other inerts, e.g., Ar, and H₂O: 0 to 70%,preferably 0 to 40%.

The literature contains many references to hydroformylation of pureethylene with syngas; literature sources include “New Syntheses withCarbon Monoxide”, Ed. J. Falbe, Springer Verlag, New York, 1980,especially the Chapter “Hydroformylation, Oxo Synthesis, RoelenReaction” by B. Cornils; and U.S. Pat. Nos. 3,527,809, 3,917,661 and4,148,830, which describe an oil-soluble phosphine-modified rhodiumcatalyst, the disclosures of all these documents being incorporatedherein by reference.

Advantageously, however, the catalyst is a cobalt catalyst, e.g.,hydrocobaltcarbonyl or one of its precursors, e.g., asdicobaltoctacarbonyl. Hydrocobaltcarbonyl is volatile and may beintroduced to the hydroformylation zone in the gas flow with the othergaseous components. The catalyst is, however, also soluble in liquidhydrocarbons and is advantageously introduced to the hydroformylationzone with the higher olefin feed. It is also possible to introduce thecatalyst in the form of a solution in an oily solvent or a mixture ofsuch solvents, for example aliphatic and aromatic hydrocarbons (e.g.,heptanes, cyclohexane, toluene), esters (e.g., dioctyl phthalate),ethers and polyethers (e.g., tetrahydrofuran, and tetraglyme), aldehydes(e.g., propanal, butanal or higher homologues), alcohols (e.g.,propanol, butanol, or higher homologues), or the condensation productsof oxo product aldehydes. Another method of introducing the catalyst tothe hydroformnylation zone is in the form of an aqueous solution of alight carboxylic acid, e.g., formic, acetic, or propionic acid, when theactive cobalt species form under the prevailing conditions.

Hydroformylation is advantageously conducted at a temperature in therange from 40 to 200° C., more advantageously from 80 to 180° C., andpreferably in the range from 90 to 155° C.

Hydroformylation may be effected in a single unit, or two or more units.In the latter case, some or all of one olefin, usually the lighter, isconveniently introduced into a downstream unit.

When a lighter olefin is introduced in a downstream unit, the liquidproduct from an upstream unit, already containing catalyst, serves as adiluent and catalyst carrier for the higher olefin, obviating thenecessity for a separate solvent.

The reaction is advantageously conducted at a pressure in the range of0.05 to 50 MPa (absolute), and preferably in the range of about 0.1 to30 MPa with a partial pressure of carbon monoxide advantageously notgreater than 50% of the total pressure.

Advantageously, the proportions of carbon monoxide, hydrogen, ethylene,and the second olefin in the feed to the oxo reactor at the foregoingpressures are maintained as follows: Co from about 1 to 50 mol %,preferably about 1 to 35 mol %; H₂ from about 1 to 98 mol %, preferablyabout 10 to 90 mol %; ethylene and the second olefin in combination fromabout 0.1 to 35 mol %, preferably about 1 to 35 mol %.

The reaction may be conducted either in a batch mode or, preferably, ona continuous basis. In a continuous mode residence times advantageouslyup to 4 hours, and preferably from 30 minutes to 2 hours, isconveniently used.

Since the catalytic oxo conversion process takes place in the liquidphase and the reactants may be gaseous compounds, a high contact surfacearea between the gas and liquid phases is desirable to avoid masstransfer limitations. A high contact surface area between the catalystsolution and the gas phase may be ensured in any suitable manner, forexample, by stirring in a batch autoclave operation. Several types ofunits used to effect hydroformylation depend on the presence of a liquidphase inside the reactor to absorb the heat of reaction and to transferit to a cooling device. With a higher olefin present in the feed thereis no need for a solvent to form this liquid phase, especially not if aportion of the lighter olefin is introduced into a downstream unit. Thisis an important advantage of the aspects of the present inventionemploying co-feeding of olefins to an oxonation zone.

In a continuous operation the reactor feed gas may be contacted with theliquid higher olefin feed containing the catalyst in, for example,reactors which effectively form a continuous-flow stirred reactor.Examples of this type of reactor are gas-lift loop reactors, usingeither an external or internal loop. Another possible reactorconfiguration is a long narrow tube, submerged in a cooling medium,whereby high contact surface area between the gas and liquid is obtainedby establishing a highly turbulent flow regime. Good contact between thecatalyst and the gas feed may also be ensured by dispersing the solutionof the catalyst on a high surface area support, a technique well knownin the art as supported liquid phase catalysis.

One of several techniques may be used for the removal of solubilizedcobalt catalyst from the reactor product. The oxo product may becontacted with an alkaline solution, for example, of sodium hydroxide,whereby the cobalt catalyst is transferred to the aqueous phase andforms a water soluble cobalt carbonyl salt. By treating this with astrong acid, for example sulphuric acid, the cobalt catalyst transfersback into its active form and becomes volatile hydrocobaltcarbonyl,which may either be returned to the hydroformylation zone with the gasfeed or absorbed in the liquid feed. This method has, however, thedisadvantage that a continuous waste water stream is being generated,which needs to be treated further before it can be discharged.Advantageously, therefore, a closed cycle method is employed. Bytreating the oxo product with air in the presence of an aqueous solutionof a light carboyxlic acid, the cobalt catalyst is transferred to theaqueous phase in the form of a water soluble salt. The resultingsolution may either be reintroduced directly in the hydroformylationzone, or sent to an outboard unit, in which the cobalt catalyst isrestored to its active form in a preformer and absorbed in the higherolefin feed. The depleted water phase is then returned and re-used torecontact the oxo product in the presence of air, as described inInternational Appication WO 93/24437, the disclosure of which isincorporated herein by reference.

Any unreacted gaseous components remaining in the oxo product areadvantageously flashed off. With the appropriate flash conditions(elevated temperature and close to atmospheric pressure), propanal maybe flashed off with this offgas and condensed out. Alternatively alkanalmay be distilled out of the degassed product.

An alkanal, e.g., propanal, separated as described above, forms thestarting material for stage (c) of this aspect of the process accordingto the invention, the aldol condensation.

The condensation of two molecules of an aldehyde to form an aldol,usually followed immediately by dehydration, to form an unsaturatedaidehyde with twice the original number of carbon atoms (or the sum ofthe carbon atoms of the two aldehydes if they are different) is wellknown, as are the conditions required to effect the condensation. Ingeneral, moderately elevated temperatures, e.g., from 40° C. to 200° C.,and pressures, e.g., from 0.01 to 2 MPa, preferably from 0.1 to 2 MPa,are used, in the presence of a catalyst, either acidic or, preferably,basic. Although organic bases may be used, a, preferably strong,inorganic base, for example an alkali metal hydroxide, is preferred,advantageously in the form of an aqueous solution. Alternatively, aheterogenous catalyst may be used, e.g., TiO₂, a basic zeolite, or achemically bound sulphonic acid, for example, that sold under the trademark Deloxan ASP by Degussa. The above conditions apply generally to thealdol process steps of the present invention; under the preferredconditions dehydration is very fast and essentially complete.

Aldolization catalyst, advantageously in the form of an aqueoussolution, is fed into the aldolization zone; since aldolization produceswater, the catalyst and some of the product water are advantageouslyseparated and the concentrated solution returned to the aldolizationzone.

Selective hydrogenation of the unsaturation of the aldol product,leaving the carbonyl group unaffected, may be carried out using any ofthe catalysts known per se for that purpose. As examples of suitablehydrogenation catalysts, there may be mentioned palladium, e.g., asupported palladium catalyst, using, for example, an alumina or carbonsupport, under relatively mild conditions, e.g., a hydrogen pressure ofup to 3, preferably between 0.5 and 2.0, MPa, and a temperature withinthe range of 80 to 200° C. optionally in an inert solvent. Suitablesolvents include aliphatic, alicyclic and aromatic hydrocarbons oroxygenated solvents, for example, alcohols and ethers. This procedure isadvantageously used if the desired end product is the correspondingacid, or if it is desired to recycle saturated aldehyde to thealdolization stage.

When the desired end product is a carboxylic acid, oxidation of anysaturated aldehyde produced by this process as a separate product may becarried out by any method known per se, i.e., practised in the art ordescribed in the literature. Oxidation is conveniently carried out usingoxygen, if desired or required in the presence of a catalyst. Ascatalyst there may be mentioned a solution containing metallic cations,e.g., copper, cobalt or manganese.

If the desired product is the saturated alcohol-then more vigoroushydrogenation conditions may if desired be employed, hydrogenation ofthe ethylenic unsaturation and reduction of the carbonyl group takingplace at the same time. For this purpose, the reaction may be carriedout under conditions and in the presence of catalyst systems known perse. For example, the catalyst may be Ni, Raney Ni, Co, partially reducedcopper oxides, copper/zinc oxides, copper chromite, alone or incombination with cobalt and nickel catalysts, Ni/Mo; Ni/W; Co/Mo or Moon carbon, optionally in their sulphided form, or combinations thereof.The conditions may include, for example, a hydrogen pressure from 2 to30 MPa and a temperature in the range of 100 to 240° C. Morespecifically, a hydrogen pressure in the range of 3.5 to 6.5 MPa, atemperature in the range of 120° C. to 240° C., and a residence timewithin the range of 0.5 to 4 hours, are preferred, conditions withinthese ranges being especially preferred if a copper chromite catalyst,preferably with a Ni or Pd catalyst in series, is used.

Dehydration of the alcohol resulting from hydrogenation of the aldolproduct may then follow. This may be accomplished, for example, atsub-atmospheric pressures, at a temperature in the range of 200° C. to350° C., over a heterogenous catalyst, e.g., alumina, advantageouslysilica-free alumina, silica, Ni on alumina, a supported mineral acid,e.g., phosphoric acid on silica or alumina, or over an acidicion-exchange resin. Alternatively, there may be used homogenousdehydration, by heating in the presence of a water-abstracting agent,e.g., sulphuric acid, a bisulphate, phosphoric acid, zinc chloride, or asulphonic, especially benzene or a naphthalene sulphonic, acid.

In a second aspect, the invention provides a process for the manufactureof a higher alcohol, the process comprising

(a) subjecting a composition comprising a lower ethylenicallyunsaturated hydrocarbon, carbon monoxide, and hydrogen tohydroformylation conditions to form a composition comprising a loweraldehyde,

(b) subjecting a first portion of the lower aldehyde-containingcomposition to aldol condensation,

(c) hydrogenating the unsaturated higher aldehyde resulting from aldolcondensation to form a lower alcohol,

(d) dehydrating the lower alcohol to form a higher unsaturatedhydrocarbon,

(e) subjecting a composition comprising the higher unsaturatedhydrocarbon, carbon monoxide, and hydrogen to hydroformylationconditions to form a composition comprising a saturated higher aldehyde,

(f) subjecting the saturated higher aldehyde and a second portion of thelower aldehyde to cross-aldolization, and

(g) hydrogenating the unsaturated cross-aldolization aldehyde product toform the higher alcohol.

As examples of lower ethylenically unsaturated hydrocarbons to be usedas feedstock to the process there may be mentioned, more especially,olefins and advantageously olefins having from 2 to 20 carbon atoms,especially ethylene.

On subjecting ethylene to the process of the second aspect of theinvention, the lower aldehyde is propanal, the unsaturated higheraldehyde resulting from aldolization is a hexenal, primarily2-methyl-2-pentenal, the lower alcohol is a hexanol, primarily 2-methylpentanol, and the higher unsaturated hydrocarbon is a hexene, primarily2-methylpentene. Oxonation of the hexene yields heptanals, primarily 3-and 5-methylhexanal, and the cross-aldolization product is a mixture ofunsaturated and saturated aldehydes in the C₃ to C₁₄ range.

In any aldolization of two or more different aldehydes, a number ofdifferent reactions may take place. In general, a smaller aldehyde ismore reactive in the conditions advantageously used in the process ofall aspects of the present invention than a larger, in part because ofits higher solubility in the aqueous catalyst-containing phase; furthera linear or a less-branched aldehyde is more reactive than a branched ormore branched aldehyde (an α-branched aldehyde being specifically lessreactive); accordingly where, as in the present aspect, it is desired toachieve “cross-aldolization” of C₇ and C₃ aldehydes, to yield a C₁₀aldehyde, primarily 2,5- and 2,7-dimethyl-2-octenals, it is desirable tominimize condensation of two C₃ molecules. To this end, the C₇ aldehydeis advantageously maintained in stoichiometric excess relative to the C₃aldehyde, and preferably in a molar ratio of at least 1.5:1.

This ratio determines the relative sizes of the first and secondportions of the lower aldehyde composition.

Hydrogenation of the cross-aldolization product yields a mixture ofproducts, including 2,5- and 2,7-dimethyloctanols.

In this second aspect of the invention, in which the preferred lowerhydrocarbon is ethylene, the composition treated in step (a) may, forexample, be obtained as described above with reference to step (a) ofthe first aspect, and the catalyst may, for example, be a rhodium orcobalt-containing catalyst also as described above. In an advantageousembodiment of the second aspect of the invention, the process isoperated in a semi-continuous manner, in which the second portion of thelower aldehyde and the higher unsaturated hydrocarbon are storedtemporarily, the feed of lower hydrocarbon to the oxonation zone ishalted, and replaced by the higher unsaturated hydrocarbon, and theresulting saturated higher aldehyde is fed together with the secondportion of the lower aldehyde to the aldolization zone. This phase maybe continued until the stores of materials are exhausted, when the firstphase of the process may be resumed. This makes it possible to use thesame oxo and aldol reactors for steps (a) and (e) and (b) and (f), ifdesired.

While for lower aldehyde manufacture a low pressure rhodium-catalysedprocess may be used, as described, for example, in U.S. Pat. Nos.4,283,562, 4,247,486, and British Patent No. 1387657, this catalystsystem is not optimal for use with branched higher olefins. Accordingly,where the same oxo reactor and process are to be used for steps (a) and(e), the higher pressure rhodium or cobalt catalyst procedures arepreferred, those being described in, for example, Falbe, J. “CarbonMonoxide in Organic Synthesis” (1970), Falbe, J. and Cornils B. inUhlmann (4th Edition, 1980) 19, 443, and Wender, I. and Pino, P.,Organic Synthesis via Metal Carbonyls (1977) 2, 233, the disclosures ofall of which are incorporated herein by reference.

If a cobalt catalyst is employed then, in all aspects of the invention,it is advantageously recovered and recycled by the procedure describedin International Application WO 93/24437, mentioned above. Thereactivated cobalt species produced by this procedure may be feddirectly to the reactor when the lower hydrocarbon is being oxonated orabsorbed in the higher hydrocarbon feed when that is being oxonated,before being fed to the reactor.

In all aspects of the invention, a substantial fraction by weight of thefinal product may originate from the syngas feedstock, and hence fromnatural gas, making for economical aldehyde, alcohol, acid, and henceester, production.

In a third aspect, the invention provides a process comprising

(a) subjecting a composition comprising a first ethylenicallyunsaturated hydrocarbon, carbon monoxide, and hydrogen tohydroformylation conditions to form a composition comprising a firstaldehyde,

(b) separately subjecting a composition comprising a secondethylenically unsaturated hydrocarbon, carbon monoxide, and hydrogen tohydroformylation conditions to form a composition comprising a secondaldehyde,

(c) combining the compositions comprising the first and secondaldehydes, subjecting the combined compositions to cross-aldolization,and hydrogenating the unsaturated cross-aldolization aldehyde product toform a higher alcohol.

In a fourth aspect, the invention provides a process comprising

(a) subjecting a composition comprising first and second ethylenicallyunsaturated hydrocarbons, carbon monoxide, and hydrogen tohydroformylation conditions to form a composition comprising at least afirst aldehyde and a second aldehyde,

(b) subjecting the aldehyde-comprising composition to aldol condensationto form a composition comprising a least a self-aldolization product ofthe first aldehyde and a cross-aldolization product of the first andsecond aldehydes,

(c) hydrogenating the aldolization product composition to form acomposition comprising alcohols,

(d) separating the resulting alcohols, and

(e) optionally dehydrating the alcohol derived from theself-aldolization of the first aldehyde and returning the resultingethylenically unsaturated hydrocarbon to hydroformylation.

Advantageously, the first hydrocarbon is a lower hydrocarbon and thesecond is a higher hydrocarbon; advantageously, as in the first aspect,the ethylenically unsaturated hydrocarbon resulting from dehydration isthe second, higher, hydrocarbon.

In a fifth aspect of the invention, which may especially conveniently becombined with the fourth, only a portion of the composition comprisingat least first and second aldehydes is fed to aldolization, and afurther portion is fed to distillation to yield separate compositionscomprising the individual aldehydes.

For example, when the first hydrocarbon is ethylene, and the second ispropene, the separative distillation yields propanal and iso- andn-butanal. Accordingly the process makes it possible to produce lightaldehydes in the same plant as and together with a wide range ofalcohols. Other examples of combinations of light hydrocarbons whichmake effective use of this possibility are combinations of any two ormore of ethylene, propene, and n- and iso-butene, yielding, for example,C₃ to C₅ aldehydes and C₃ to C₁₅ alcohols.

In a sixth aspect, which may especially conveniently be combined withthe fifth, a mixture of first and second aldehydes is subjected toaldolization, and a portion of the resulting lower unsaturated aldehydeis returned to the aldolization zone. This facilitates the production ofa wide range of aldehydes, and hence alcohols, downstream.

For example, when the first and second hydrocarbons are ethylene andpropene, the lower unsaturated aldehyde is 2-methyl-2-pentenal,cross-aldolization of this with the first and second aldehydes and theirself- and cross-aldolization products yields, on hydrogenation, alcoholswith from 6 to 10 carbon atoms, while unreacted lower and higheraldehydes yield alcohols with three and four carbon atoms.

In a seventh aspect, particular use is made of the fact that underoxonation conditions, especially when carried out under high pressure inthe presence of a rhodium or cobalt carbonyl catalyst, e.g., thehydridotetracarbonyl or di(cobalt)octacarbonyl, isomerization of thedouble bond tends to occur. This makes it possible to employ olefinfeedstocks which, prima facie, would not be amenable to oxonation and,in turn, makes it possible to employ, as a source for producing anolefin feedstock by dehydration, an alcohol that similarly would appearto be unsuitable.

For example, in accordance with rules set out in a paper by Keulemans,et al., Rec. Trav. Chim Pay-Bas, 67, 298 (1948) 2,3-dimethylbutene-2 isnot capable of adding a carbonyl group at any carbon atom (each methylgroup is adjacent to a quaternary carbon atom, a forbidden accesspoint). In practice, however, double bond isomerization allowshydroformylation to take place at a methyl group, albeit at a reactionrate slower than for other isomers. This isomerization makes possiblethe use of secondary and tertiary alcohols, as well as primary alcohols,as olefin sources. Since such materials are often produced asby-products in other processes, for example, 2-propanol, sec- andt-butanol, and are presently regarded as of relatively low value, aprocess that can use them as starting materials has considerableadvantages.

In accordance with the seventh aspect, therefore, the invention providesa process in which at least two ethylenically unsaturated hydrocarbons,each advantageously having from 2 to 21 carbon atoms, arehydroformylated, the resulting aldehydes are at least partiallyseparated, at least one aldehyde is aldolized, the resulting unsaturatedaldehyde is or aldehydes are hydrogenated to form saturated alcohols,the alcohols are at least partially separated, and at least one alcoholis dehydrated to an ethylenically unsaturated hydrocarbon and subjectedto hydroformylation, the alcohol subjected to dehydration being aseparated alcohol, an alcohol originating from outside the process, or amixture of such alcohols.

As examples of processes in accordance with this aspect, there may bementioned:

A. 2-methylpropanol, a by-product from n-butanol production, isdehydrated to isobutene and co-fed with ethylene to oxonation. Alportion of the resulting 3-methylbutanal and propanal is aldolized toform a mixture of C₆, C₈ and C₁₀ unsaturated aldehydes, and the aldolproduct combined pith another portion of C₃ and C₅ aldehydes,hydrogenated, and distilled to form primary alcohols in the C₃ to C₁₀range.

B. If, in A above, more C₉ is required, the C₈ alcohol may be dehydratedand recycled, or 3-octanol from an external source may be dehydrated,oxonated, hydrogenated to C₉ alcohol and recovered.

C. A mixture of primary, secondary, and tertiary C₅ alcohols may bedehydrated, oxonated, and the resulting C₆ aldehydes separated. Theprimary C₆ aldehyde is aldolized, the C₁₂ aldehyde is hydrogenated togive a mixture of C₁₂ primary alcohols.

D. A mixture of C₃ to C₅ alcohols from methane carbonylation may bedehydrated, oxonated, cross-aldolized, hydrogenated and distilled togive a range of C₄ to C₁₂ alcohols.

E. Ethanol, e.g., from fermentation of vegetable material, and2-methyl-pentanol may be dehydrated, the resulting olefins are oxonatedand aldolized in admixture and hydrogenated to yield n-propanol,2-methylpentanol (part of which may be returned to dehydration) and C₇,C₁₀, and C₁₄ alcohols.

F. A mixture of 2-methylbutenes may be oxonated, part of the resultingC₆ aldehyde aldolized, and the whole hydrogenated to C₆ and C₁₂alcohols.

Dehydration of the C₁₂ alcohol, oxonation of the resulting olefin andpart cross-aldolized with C₆ aldehyde and hydrogenated, yields C₁₃ andC₁₉ alcohols. This procedure may be repeated as required.

It will be appreciated that it is within the scope of the invention toemploy all or part of one aspect in conjunction with all or part of anyother or others to the extent that the procedures are compatible.

As indicated above, the saturated alcohols produced by the processes ofthe invention are valuable intermediates in the manufacture of esterssuitable for use as plasticizers and synthetic lubricants, lubricantcomponents, hydraulic fluids and drilling fluids, by reaction withappropriate acids, for example, by reaction with monobasic or polybasic,e.g., tribasic or more especially dibasic acids, or where appropriatetheir derivatives, e.g., anhydrides, or by transesterification withother, e.g., methyl, esters. The acids produced by the process of theinvention have similar uses. The branched C₇ acid produced by theprocess of the invention has especial utility in the formation, with apolyol, of an ester suitable for use as a refrigerant lubricant.

The acid used for forming an ester with an alcohol produced by theprocess of the invention may be inorganic or organic; if the latter,carboxylic acids are preferred. Among organic acids, aromatic acids arepreferred for plasticizer manufacture, although aliphatic acids are alsoemployed. As examples of acids, phthalic (1,2-benzene-dicarboxylic),isophthalic, terephthalic, adipic, fumaric, azelaic, sebacic,trimellitic, pyromellitic, and phosphoric acids may be mentioned. Esterswith monobasic and dibasic acids are preferred for lubricants andlubricant components; advantageously the resulting esters contain from15 to 40 carbon atoms.

The esters may be produced by methods known per se or described in theliterature from the alcohol and the relevant acid or, preferably, whereappropriate, the anhydride, optionally in the presence of a solvent.Elevated temperatures and reduced pressures are generally employed todrive the reaction toward completion by removal of the water produced.Catalysts may be employed. Suitable catalysts include, for example, atitanium catalyst e.g., a tetraalkyl titanate, especiallytetra-iso-propyl or tetraoctyl ortho titanate, or a sulphonic acid,e.g., p-toluene sulphonic acid or methylsulphonic acid. Any catalystpresent in the reaction product may be removed by alkali treatment andwater washing. Advantageously, the alcohol is used in slight, e.g.,about 25%, molar excess relative to the number of acid groups in theacid.

The esters may be used as a plasticizer for numerous polymers, forexample, cellulose acetate; homo- and copolymers of aromatic vinylcompounds e.g., styrene, or of vinyl esters with carboxylic acids e.g.,ethylene/vinyl acetate copolymers; halogen-containing polymers,especially vinyl chloride homo- and copolymers, more especially thosecopolymers with vinyl esters of carboxylic acid, esters of unsaturatedcarboxylic acids and/or olefins; nitrile rubbers; and post-chlorinatedvinyl chloride polymers. Poly(vinyl chloride) is of especial interest.

The proportion of plasticizer may vary within wide limits, but isgenerally 10 to 200 parts by weight per 100 parts of polymer, moreespecially 20 to 100 parts per 100.

The esters may be used alone as plasticizer, or in admixture with otherplasticizers, for example, dibutyl, dipentyl, dihexyl, diheptyl,dioctyl, dinonyl, didecyl, diundecyl, didodecyl, ditridecyl phthalates,trimellitates or adipates, or butyl benzyl phthalate, or mixturesthereof. If used in admixture, it is the total proportion of plasticizerthat is advantageously within the ranges given above.

The plasticized polymeric compositions may be made up in numerous formsand have various end-uses. For example, they may be in the form of adryblend, a paste, or a plastisol, depending on the grade of the resinemployed. They may be used, for example, as coatings, in dipping,spraying, rotational moulding, or self-supporting films and sheets, andmay readily be foamed. End uses include flooring materials, wallcoverings, moulded products, upholstery materials, leather substitutes,electrical insulation and coated fabrics.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the process of the invention will now bedescribed in greater detail by way of example only with reference to theaccompanying drawings, in which:

Each of FIGS. 1 to 6 is a schematic flow diagram of a process for themanufacture of at least one aldehyde, alcohol, or acid from an olefin.

Referring now to FIG. 1, ethylene, syngas and recycled 2-methylpenteneare fed to an oxonation reactor 2. A cobalt catalyst is absorbed in the2-methylpentene feed. The catalyst is separated from the mixed aldehydeproduct, by contacting it with air in the presence of a light carboxylicacid, sent to an outboard unit 34 and returned to the reactor in theliquid feed. The demetalled product is fed through a line 4 to a firstdistillation column 5, where lights are taken off overhead and thebottoms product fed to a second distillation column 7. Here, propanal istaken off overhead and the bottoms product fed to a third distillationcolumn 9, where light byproducts are taken off overhead and the bottomsproduct is fed to a fourth distillation column 10.

The propanal from the second column overhead is fed to an aldol reactor15, from which the unsaturated C₆ aldehyde is fed to a hydrogenationreactor 16. The saturated C₆ alcohol-containing product is fed to afifth distillation column 17, the purified alcohol product being takenoff overhead. If desired, part of the alcohol product may be recovered,or it may all be dehydrated in a reactor 20 and fed through a line 1back to the oxo reactor 2.

From the fourth column 10, C₇-aldehyde is taken off overhead and fed toa hydrogenation reactor 22, where it is converted to a C₇ alcohol. Afterpassing through a sixth distillation column 30 where it is separatedfrom lights and a seventh distillation column 32, where it is separatedfrom heavies, a branched C₇ alcohol is recovered.

The alcohol produced is a mixture of isomers; predominantly, however, itwill be 5-methylhexanol and 3-methylhexanol, with minor proportions of2,4-dimethylpentanol and traces of 2-ethyl-3-methylbutanol.

In broken lines, there is shown an optional additional process in whichthe product from the aldol reactor 15 is fed to a selectivehydrogenation reactor 36 and converted to the corresponding saturatedaldehyde, then oxidized by oxygen-enriched air in an oxidation reactor38 to the corresponding acid. Although shown in FIG. 1 only, the optionto take unsaturated aldehydes from the aldol reactor and convert them tothe corresponding acids by selective hydrogenation and oxidation isavailable in all embodiments of the invention, including thosesubsequently described.

In an alternative procedure, not illustrated, the C₇ aldehyde from thecolumn 10 is oxidized, for example with oxygen-enriched air, in anoxidation reactor akin to reactor 38. The acid product from either ofthese oxidation reactors is desirably distilled to remove lights andheavies.

Referring now to FIG. 2, in FIG. 2a, there is shown an example of theprocess of the second aspect of the invention in its first phase, whileFIG. 2b shows its second phase.

In the first phase, the feedstock comprises hydrogen and carbon monoxide(syngas) and ethylene, which feedstock is fed to an oxo reactor 51together with a cobalt catalyst. Exemplary molar proportions are, permole of ethylene, 1 to 4 moles of hydrogen and 1 to 2 moles of carbonmonoxide, typical conditions being: temperature 100 to 150° C., pressure20 to 30 MPa, catalyst 0.05 to 0.1% by weight cobalt as hydrido cobalttetracarbonyl. The reactor product is cooled, degassed, the gases beingrecycled, and decobalted by contact with air in the presence of anaqueous solution of a light carboxylic acid. The product is then fed toa first distillation column 53, and propanal is recovered overhead. Thepropanal is divided into portions, a first being fed to an aldol reactor55, and a second sent to a holding tank 57, the second portion typicallyrepresenting from 30 to 50% of the total.

The first portion is converted in the reactor 55 (typical conditions:strong base or acid catalyst) to unsaturated C₆ aldehydes, primarily2-methyl-2-pentenal, the product being fed to a second distillationcolumn 59, where unconverted propanal is recycled to the reactor 55,heavies removed as bottoms product, and unsaturated C₆ aldehydes takenoff as a sidestream and fed to a hydrogenation zone 61 (typicalconditions: CuCr catalyst in combination with Ni or Pd catalyst; 120 to220° C. and medium pressure). The resulting alcohols are then fed to adehydration unit 63 (typical conditions: alumina catalyst, 200 to 350°C., subatmospheric pressure), and the dehydrated product, hexenes,primarily 2-methylpentene, sent to a holding tank 65.

In the second phase, the feedstock to the oxo reactor 51 comprisessyngas and hexenes (the conditions being similar to those used in thefirst phase except that 0.1 to 0.5% by weight of cobalt catalyst isused) and the desired product, C₇ aldehydes, primarily 3-methylhexanal,is recovered as a sidestream from the column 53 and fed, together withpropanal from the tank 57, to the aldol reactor 55. As indicated above,the ratio of the feedstreams is selected to maximize unsaturated C₁₀aldehyde production among the product mix of C₃ to C₁₄ materials. Themixture is fed to the hydrogenation reactor 61, and the resultingalcohol-containing stream is fed to the second column 59 together with,if desired, the bottoms product from the first column 53. From thecolumn 59, propanol is taken overhead to a tank 66, 2-methylpentanol istaken as a first sidestream to dehydration unit 63 and thence to a tank65, C₇ alcohols (primarily 3-methylhexanol) are taken as a secondsidestream to a tank 67, and C₁₀ alcohols, primarily2,5-dimethyloctanol, taken as a third sidestream to a tank 69.

This second phase is continued until the supplies from tanks 57 and 65are exhausted, when the process is switched back to the first phase.

Referring now to FIG. 3, into first and second oxonation reactors 101and 103, syngas and catalyst are fed. Into the first reactor 101 thefeedstock is ethylene, while 2-methylpentene is fed from a storage tank105 to the second reactor 103. The propanal-containing product from thefirst reactor 101 is demetalled and fed to a first distillation column107, pure propanal being taken off overhead and any propanol being takenoff as a sidestream. Similarly, a C₇ aldehyde-containing product ispassed from the reactor 103 to a second distillation column 109, any C₇alcohol being taken off as a second sidestream. The aldehydes are fed toan aldol reactor 111, the unsaturated aldehyde product then beinghydrogenated, together with the alcohol-containing sidestreams, in ahydrogenation unit 113. The alcohol product from the unit 113 is passedto a further distillation column or columns represented schematically bycolumn 114 where it is separated. Reference numeral 114 may represent abatch procedure in which products are recovered sequentially. When2-methylpentanol is taken off it is divided, and a portion passed to adehydration unit 115, the resulting 2-methylpentene being recycled tothe storage tank 105. C₇, C₁₀ and C₁₄ alcohols are taken offsubsequently. Alternatively, more than one column may be used, eithersequentially or making a first heart cut and separating individual cuts.

Referring now to FIG. 4, the procedure is generally similar to that ofFIG. 3, with the exception that a single oxonation reactor 151 is used,and that catalyst is returned to the reactor from an outboard unit 160by being entrained in the 2-methylpentene from a storage tank 155.Treatment in aldol reactor 161, hydrogenation unit 163, distillationcolumn 164, dehydration unit 165, and recycling of 2-methylpentene tothe storage tank 155 are identical to that described above for FIG. 3.

Referring now to FIG. 5, into a single oxonation reactor 201 are fedsyngas, ethylene, propene, and catalyst, examples of typical conditionsand reaction proportions being ethylene:propene—1:10 to 10:1 by weight,H₂/CO syngas ratio 0.5:1 to 2:1, low or high pressure Rh catalysis orhigh pressure Co catalysis, with a heavy diluent for temperaturecontrol, as catalyst carrier, or both. After the oxo product isdemetalled and degassed, also removing light olefins and paraffins, theproduct is fed to a first distillation column 203. Here all lightaldehydes are taken off overhead. When a substantial quantity of alcoholis being formed in the reactor 201, the bottoms product of the column203 may be worked up in a second column 204 where it is separated fromany heavy diluent and heavies formed in the oxonation reaction. Part ofthe overhead stream from the column 203 is passed to three furtherdistillation columns, 205, 207, and 209, whence, respectively, propanal,i-butanal and n-butanal are recovered overhead.

A second part of the light aldehyde stream is fed to an aldolizationreactor 211, the aldol product being fed to a sixth distillation column213. The overhead from this distillation column 213, containingunreacted light aldehydes, may be fed to the third distillation column205 or recycled, while the bottoms product is passed to the seventhcolumn 215. From here, the overhead may be recycled or mixed with thebottoms product from the fifth column 209, which is mixed with thebottoms product from the seventh column 215 which is being fed to ahydrogenation unit 217 as is the overhead product from the second column204. The hydrogenation product is then fed to an eighth distillationsection 220, whence a variety of alcohols from C₃ to C₁₀, with theexception of C₅, is recovered. The section 220 may be a single column,using batch operation, or multiple columns, operated continuously,either in a sequential operation or by making a first heart cut,followed by separation of individual cuts.

The preponderant isomers of the C₇ to C₁₀ alcohols are

C₇:2,4-dimethylpentanol, 2-ethylpentanol, 2-methylhexanol

C₈:2-ethylhexanol, 2-ethyl-4-methylpentanol

C₉:2,4-dimethylheptanol

C₁₀:2-ethyl-4-methylheptanol.

Referring now to FIG. 6, at least one olefin is fed by a line 251 to anoxonation reactor 253, where it is caused to react with syngas. Theolefin is fed in admixture with a further olefin or olefins from a line255. Part of the resulting aldehyde product mixture is passed to adistillation column 257, a second part optionally being taken offthrough a line 259. The separated aldehyde products are passed to two ormore of storage tanks 261/3 to 261/21, as appropriate to the boilingpoint or range, unreacted material being taken off overhead, and thebottoms optionally fed to the line 259. Material from one or more of thetanks 261 is fed to an aldolization reactor 265, a part optionally beingfed to the line 259. Aldolization product is fed to a hydrogenation unit207 together with any content of the line 259, and the hydrogenationproduct fed to a second distillation column 269. The separated alcoholsare passed to one or more of storage tanks 271/3 to 271/21, whenceproduct may be recovered. As required, the contents of one or more ofthe tanks 271 may be fed through a line 273 to a dehydration unit 275,where it may be combined as required with alcohol from a separatesource. The resulting olefin is fed by the line 255 to oxonation.

What is claimed is:
 1. A process for the manufacture of at least onehigher aldehyde, said process comprising: hydroformylating ethylene anda second ethylenically unsaturated hydrocarbon to form a compositioncontaining propionaldehyde and a second aldehyde, wherein said secondaldehyde contains less than 2 hydrogen atoms bonded to the alpha carbonatom; and subjecting the propionaldehyde and second aldehyde containingcomposition to cross-aldolization to form a cross-aldplization product,wherein at least a portion of said propionaldehyde undergoescross-aldolization with said second aldehyde and said cross-aldolizationproduct further undergoes dehydration to produce an unsaturatedaldehyde.
 2. A process as claimed in claim 1, wherein the ethylene andsecond ethylenically unsaturated hydrocarbon are hydroformylated inadmixture to give a composition comprising propionaldehyde and thesecond aldehyde.
 3. A process as claimed in claim 1, wherein said secondethylenically unsaturated hydrocarbon is a C₆ to C₁₂ olefin.
 4. Aprocess for the manufacture of organic compounds, comprising:hydroformylating a composition comprising ethylene and 2-methylpentene;separating a portion of the resulting C₃ aldehyde and C₇ aldehydes;cross-aldolizing at least a portion of the C₃ aldehyde and C₇ aldehydesfollowed by dehydration to form a composition comprising an unsaturatedC₆ aldehyde and C₁₀ aldehydes; hydrogenating at least a portion of theresulting C₆ and C₁₀ unsaturated aldehyde composition to form acomposition comprising the corresponding alcohols; separating at least aportion of the C₆ alcohol from the alcohol composition; dehydrating theC₆ alcohol to form a composition comprising 2-methylpentene; returningthe 2-methylpentene comprising composition to the hydroformylationstage; and recovering a product comprising a C₇ aldehyde.
 5. A processas claimed in claim 4, further comprising selectively hydrogenating afurther portion of the unsaturated C₆ aldehyde to a saturated C₆aldehyde.
 6. A process as claimed in claim 5, wherein at least a portionof said saturated C₆ aldehyde is oxidized to form a carboxylic acid. 7.A process for the manufacture of an alcohol, comprising: (a) subjectingethylene to hydroformylation conditions to form propionaldehyde; (b)subjecting a first portion of the propionaldehyde to aldol condensationfollowed by dehydration to form an unsaturated C₆ aldehyde; (c)hydrogenating the unsaturated C₆ aldehyde resulting from aldolcondensation to form a C₆ alcohol; (d) dehydrating the C₆ alcohol toform a C₆ unsaturated hydrocarbon; (e) subjecting a compositioncomprising the C₆ unsaturated hydrocarbon, carbon monoxide, and hydrogento hydroformylation conditions to form a composition comprising asaturated C₇ aldehyde; (f) subjecting the saturated C₇ aldehyde and asecond portion of propionaldehyde to cross-aldolization, wherein thecross-aldolization product further undergoes dehydration to produce anunsaturated aldehyde; and (g) hydrogenating the unsaturatedcross-aldolization aldehyde product to form a higher alcohol.
 8. Aprocess as claimed in claim 7, wherein said higher alcohol isesterified.
 9. A semi-continuous process for the manufacture of analcohol, comprising: (a) alternately subjecting ethylene and anunsaturated C₆ olefin to hydroformylation conditions to formpropionaldehyde and a saturated C₇ aldehyde; (b) subjecting a firstportion of the propionaldehyde to aldol condensation followed bydehydration to form an unsaturated C₆ aldehyde; (c) hydrogenating theunsaturated C₆ aldehyde resulting from aldol condensation to form a C₆alcohol; (d) dehydrating the C₆ alcohol to form a C₆ unsaturatedhydrocarbon; (e) recycling the C₆ unsaturated hydrocarbon tohydroformylation step a; (f) subjecting the saturated C₇ aldehydeproduced in step a and a second portion of propionaldehyde tocross-aldolization, wherein the cross-aldolization product furtherundergoes dehydration to produce an unsaturated aldehyde; and (g)hydrogenating the unsaturated cross-aldolization aldehyde product toform a higher alcohol.
 10. A process as claimed in claim 1, comprising:separately hydroformylating the ethylene and the second ethylenicallyunsaturated hydrocarbon; combining the resulting compositions comprisingthe propionaldehyde and second aldehyde; subjecting the combinedcompositions to cross-aldolization, followed by dehydration; andhydrogenating the unsaturated cross-aldolization aldehyde product toform a higher alcohol.
 11. A process as claimed in claim 1, wherein saidcross-aldolization product reaction is accompanied by a self-aldolcondensation of the said propionaldehyde, said process furthercomprising: hydrogenating said cross-aldolization product to form acomposition comprising alcohols; and separating the resulting alcohols.12. A process as claimed in claim 11, further comprising dehydrating thealcohol derived from the self-aldolization of the propionaldehyde andreturning the resulting ethylenically unsaturated hydrocarbon tohydroformylation.
 13. A process as claimed in claim 1, wherein theethylene and second ethylenically unsaturated hydrocarbon arehydroformylated in admixture, the propionaldehyde and second aldehydeare at least partially separated, further comprising: hydrogenating theunsaturated aldehyde resulting from dehydration to form saturatedalcohols; separating the resulting saturated alcohols at leastpartially; dehydrating at least one saturated alcohol to a thirderhylenically unsaturated hydrocarbon; and hydroformylating said thirdethylenically unsaturated hydrocarbon to a third aidehyde.
 14. A processas claimed in claim 1, wherein only a portion of the compositioncomprising propionaldehyde and second aldehyde is fed to aldolization,and a further portion is fed to distillation to yield separatecompositions comprising the individual aldehydes.
 15. A process asclaimed in claim 1, wherein hydroformylation is carried out in thepresence of a cobalt catalyst.
 16. A process as claimed in claim 8,wherein the ester is made by reaction with a dibasic acid or ananhydride thereof.
 17. A process as claimed in claim 1, wherein aportion of the resulting self condensation product of propionaldehyde isreturned to the aldolization zone.
 18. A process as claimed in claim 1,further comprising selectively hydrogenating a portion of theunsaturated second aldehyde to form a corresponding saturated higheraldehyde and oxidizing the saturated higher aldehyde to form acorresponding higher acid.